This document relates to porous metal oxide particles and composites made from gels.
Porous metal oxide particles have been produced by extracting the liquid component of certain gels through methods such as supercritical carbon dioxide drying, freeze-drying, and the use of a spring-back effect during the ambient drying of surface-modified gels. These methods allow liquid in the gel to be removed without causing the solid matrix in the gel to collapse. Porous metal oxide particles have also been prepared by the use of organic templates which are removed by calcination or dissolution. These methods can be costly, time-consuming, environmentally hazardous, or limited to certain metal oxides, such as silica. Some drying methods result in fragile porous materials with limited application.